The present invention relates to prosthetic devices, and more particularly, to a prosthetic limb pyramidal link-plate assembly which provides for infinite rotational adjustments.
As shown in FIG. 1a, a conventional pyramidal link-plate 10 will have a frustopyramidal, four-sided boss 12 projecting from a dome-shaped, or a spherically convex base 14, which in turn projects from a plate member 16. The plate member 16 will typically include four screw or bolt-receiving, through-holes 18 corresponding to a standard (within the industry) four-hole pattern. The conventional pyramidal link-plate 10 is primarily based upon the "Adjustable Link" described in U.S. Pat. No. 3,659,294 to Glabiszewski, the disclosure of which is incorporated herein by reference.
As shown in FIG. 1b, a prosthetic limb 20 for a transfemoral amputee will include a prosthetic limb socket 22 for receiving the wearer's residual limb, a knee joint assembly 24, a first pylon component 23 between the prosthetic limb socket and the knee joint assembly, interconnection components 26 for coupling the first pylon 23 to the prosthetic limb socket 22, interconnection components 27 for coupling the first pylon to the knee joint assembly 24, an ankle/foot assembly 28, and a second pylon 29 coupled between the knee joint assembly 24 and the ankle/foot assembly 28. The interconnection components 26 may consists of a locking or suction assembly 30 (such as a Shuttle Lock component or a ProSeal component commercially available from Prosthetic Design, Inc.) positioned within a distal end of the prosthetic limb socket 22, the conventional pyramidal link-plate 10, and an annular coupling-socket adapter 32 for coupling the first pylon 23 to the distal boss 12 of the pyramidal link-plate 10. Likewise, the interconnection components 27 may consist of the conventional pyramidal link-plate 10 mounted to the knee-joint assembly and another annular coupling-socket adapter 32 for coupling the first pylon 23 to the distal boss 12 of the pyramidal link-plate 10. The plurality of set screws 33 extend radially and downwardly against the distal boss 12 of the pyramidal link-plate 10 and are tightened to securely mount the pyramidal link-plate 10 (and the respective prosthetic limb components fastened thereto) to the coupling-socket adapter 32 (and the first pylon 23).
In fitting prosthetic limbs to patients, it is often necessary for the prosthetist to modify the alignments and orientations of the various prosthetic limb components with respect to each other during the initial fitting or after the patient has worn the prosthetic limb for a period of time. The first pylon 23 is typically capable of being rotatably adjusted with respect the coupling-socket adaptors. However, with certain transfemoral amputees, the distance between the distal end of the patient's residual limb and the patient's natural knee center is very short; and if the combined length of the components between a prosthetic limb socket and the prosthetic knee joint is greater than the distance between the distal end of the patients residual limb and the patient's natural knee center, then the prosthetist may be forced to eliminate the first pylon 23. Otherwise the knee center on the prosthetic side will be too low, thus causing gate deviation.
When the first pylon 23 is eliminated, the means to rotatably adjust the various prosthetic limb components is also lost. Accordingly, there are existing pyramidal link-plate components which offer sliding and/or rotating capabilities to such components. The disadvantage with the conventional sliding and/or rotating pyramidal link-plate components is that to provide such adjustability, the profile and/or the length of the component must be increased. Other rotatably adjustable pyramidal link-plate components only allow finite or incremental rotation and are difficult to adjust.
For example, one known rotatably adjustable pyramidal link-plate assembly includes a dome shaped component having the pyramidal boss extending from its apex, where the dome shaped component includes an upwardly facing (i.e., facing in towards the apex of the dome), serrated, annular ring positioned around an outer circumference of the base of the dome. The assembly also includes a planar base plate component having four screw-holes extending therethrough arranged in a standard four-hole pattern. The planar base plate also has a central hole, sized for receiving the dome portion of the dome shaped component therethrough. On the underside of the planar base plate, encircling the central hole, is a serrated, annular ring adapted to engage with the upwardly facing serrated, annular ring of the dome shaped component when the dome shaped component is inserted through the underside of the central hole. When the two components are assembled, and installed onto a prosthetic limb component by tightening four screws extending through the screw-holes, the two components are rotationally locked with respect to each other. To rotatably adjust the two components with respect to each other, the four screws must be loosened enough to allow the base plate component to be lifted from the dome shaped component to a sufficient extent so that the two serrated rings disengage from one another. Once the rotational adjustment is made, the screws are tightened again.
One disadvantage with this design is that the serrations, or teeth, allow for only finite (e.g. 5 or 6 degree increments) rotational adjustments. Additionally, it is often-times difficult to have access to the four screws extending through the base plate component (especially when the prosthetic limb socket and knee joint assembly are positioned in close proximity to one another). To access the four screws in such a situation, the adjustable pyramid link-plate assembly must first be separated from the female coupling-socket adapter. Accordingly the prosthetist will essentially have to disassemble the prosthetic limb to adjust rotational alignment.
Accordingly, there is a need for a prosthetic limb pyramidal link-plate component that provides rotatable adjustment to the prosthetic limb, yet does not significantly increase the profile or length of the attachment of the interconnection components; there is a need for a prosthetic limb pyramidal link-plate component that provides for infinite rotational adjustments; and there is a need for a prosthetic limb pyramidal link-plate component that does not require disassembly of the various interconnection components to allow for rotational adjustments.